Field of the Disclosure
The present disclosure relates generally to optical communication networks and, more particularly, to reach extension of multi-carrier channels using unequal subcarrier spacing.
Description of the Related Art
Telecommunications systems, cable television systems and data communication networks use optical networks to rapidly convey large amounts of information between remote points. In an optical network, information is conveyed in the form of optical signals through optical fibers. Optical networks may also include various network nodes such as amplifiers, dispersion compensators, multiplexer/demultiplexer filters, wavelength selective switches, couplers, etc. to perform various operations within the network.
Optical superchannels are an emerging solution for transmission of signals at 400 Gb/s and 1 Tb/s data rate per channel, and hold promise for even higher data rates in the future. A typical superchannel includes a set of subcarriers that are frequency multiplexed to form a single wavelength channel. The superchannel may then be transmitted through an optical network as a single channel across network endpoints. The subcarriers within the superchannel are tightly packed to achieve high spectral efficiency. The transmission reach of a superchannel may be limited by various factors.
Another technique for transmission of optical signals is the use of a multi-carrier channel (also referred to as subcarrier multiplexing (SCM) or Nyquist frequency division multiplexing (Nyquist-FDM)). A multi-carrier channel is generated at a transmitter for an optical channel but with division of the optical channel into a given number of subcarriers. As with superchannels, the transmission reach of a multi-carrier channel may be limited by various factors, such as certain nonlinear effects that undesirably increase noise.